In a small saucepan combine 1/2 cup soy sauce, 1/4 cup water, 1/4 cup honey, 1 tablespoon rice vinegar, 2 teaspoons chili flakes, 1 teaspoon minced garlic, 1 teaspoon grated ginger, and 1 teaspoon sesame oil; whisk to blend.
Place the saucepan over medium heat and stir occasionally until the honey is dissolved and the mixture is warm (do not let it boil).
In a separate small bowl, whisk 1 tablespoon cornstarch with 2 tablespoons cold water until completely smooth (no lumps).
Once the sauce is warm and beginning to simmer, slowly pour the cornstarch slurry into the saucepan while stirring continuously to prevent lumps.
Bring the mixture to a gentle simmer and cook, stirring frequently, until the sauce thickens, about 3–4 minutes.
Remove from heat and let the sauce cool slightly before using or storing.